Lens barrel and image taking apparatus

1. A lens barrel which accommodates a shooting lens having a plurality of lens groups including at least a variable-power lens group and a focus-adjusting lens group, which can change a barrel length between an accommodated state having a relatively short barrel length and a shooting state having a relatively long barrel length, the lens barrel comprising:

a lens retracting mechanism which retracts at least one of the lens groups from a shooting optical axis when the lens barrel is retracted to be in the accommodated state, and a lens advancing mechanism which advances the lens group retracted when the lens barrel is retracted to the shooting optical axis when the lens barrel advances to be in the shooting state,

wherein the shooting lens forms a shooting optical system by the remaining lens group among the plurality of lens groups excluding the lens group retracted from the shooting optical axis when the lens barrel is in the accommodated state.

2. The lens barrel according to claim 1 , wherein the shooting lens forms a fixed focus shooting optical system by the remaining lens group.

3. The lens barrel according to claim 1 , wherein the shooting lens comprises three groups, i.e., a front lens group, a rear lens group and a focus lens arranged in this order from forward of the optical axis direction, the focal length of the shooting lens can be changed, and the focus is adjusted by moving the focus lens,

wherein the lens barrel further comprises a lens advancing/retracting mechanism including the lens retracting mechanism and the lens advancing mechanism,

wherein the lens advancing/retracting mechanism retracts the rear lens group from the shooting optical axis when the lens barrel is retracted to be in the accommodated state, and

wherein the shooting lens forms a shooting optical system by the front lens group and the focus lens when the lens barrel is in the accommodated state.

4. The lens barrel according to claim 3 , wherein the front lens group is a lens group having a positive refractive force, the rear lens group is a lens group having a negative refractive force, and the focus lens is a lens group having a positive refractive force.

5. The lens barrel according to claim 1 , further comprising a light amount control member which controls an amount of light passing through the shooting lens, wherein the light amount control member retracts from the shooting optical axis together with the lens group which retracts from the shooting optical axis when the lens barrel is retracted, and when the lens barrel advances to be in the shooting state, the light amount control member advances to the shooting optical axis together with the lens group retracted when the lens barrel is retracted.

6. The lens barrel according to claim 1 , further comprising a light amount control member which controls an amount of light passing through the shooting lens, wherein the light amount control member stays on the shooting optical axis even when the lens barrel is in the accommodated state.

7. The lens barrel according to claim 1 , wherein the shooting lens comprises two lens groups, i.e., a front lens group and a rear lens group arranged in this order from forward of the optical axis direction,

wherein the lens barrel further comprises a lens advancing/retracting mechanism including the lens retracting mechanism and the lens advancing mechanism,

wherein the lens advancing/retracting mechanism allows a first lens group comprising one of the two lens groups to retract from the shooting optical axis when the lens barrel is retracted to be in the accommodated state, and allows the first lens group retracted when the lens barrel is retracted to advance to the shooting optical axis when the lens barrel is advanced to be in the shooing state, and

wherein the shooting lens forms a shooting optical system by a second lens group of the two lens groups when the lens barrel is in the accommodated state.

8. The lens barrel according to claim 7 , further comprising a correction lens which advances on the shooting optical axis and corrects aberration of the second lens group when the lens barrel is in the accommodated state, and which is retracted from the shooting optical axis when the lens barrel is in the shooting state,

wherein the shooting lens forms a shooting optical system by the second lens group and the correction lens when the lens barrel is in the accommodated state.

9. The lens barrel according to claim 7 , wherein the lens advancing/retracting mechanism retracts the front lens group from the shooting optical axis when the lens barrel is retracted to be in the accommodated state, and advances the front lens group to the shooting optical axis when the lens barrel is advanced to be the shooting state.

10. The lens barrel according to claim 1 , wherein the shooting lens comprises four lens groups, i.e., a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in this order from forward of the optical axis direction,

wherein the lens barrel comprises a lens advancing/retracting mechanism which retracts at least one of the third lens group and the fourth lens group from the shooting optical axis when the lens barrel is retracted to be in the accommodated state, and which advances the lens group retracted when the lens barrel is in the accommodated state to the shooting optical axis when the lens barrel advances to be in the shooting state, and

wherein the shooting lens forms a shooting optical system by the remaining lens group among the four lens groups excluding the lens group retracted from the shooting optical axis when the lens barrel is in the accommodated state.

11. The lens barrel according to claim 10 , wherein the lens advancing/retracting mechanism retracts both the second lens group and the fourth lens group from the optical axis when the lens barrel is retracted to be in the accommodated state, and advances the second lens group and the fourth lens group retracted in the accommodated state when the lens barrel advances to be in the shooting state, and

wherein the shooting lens forms a shooting optical system by the remaining lens group among the four lens groups excluding the second lens group and the fourth lens group retracted from the shooting optical axis when the lens barrel is in the accommodated state.

12. The lens barrel according to claim 10 , wherein the shooting lens forms a fixed shooting optical system by the remaining lens group when the lens barrel is in the accommodated state.

13. The lens barrel according to claim 10 , wherein the first lens group, the second lens group, the third lens group, and the fourth lens group have a positive refractive force, a negative refractive force, a positive refractive force, and a positive refractive respectively.

14. The lens barrel according to claim 1 , wherein the shooting state is a state in which an image is formed by using all the plurality of lens groups comprising the shooting lens, and the accommodated state is a state in which the barrel length is shorter than the shortest barrel length in the shooting state.

15. An image taking apparatus which takes a picture by capturing a subject light, comprising:

a shooting lens which has a plurality of lens groups including at least a variable-power lens group and a focus-adjusting lens group; and

a lens barrel which accommodates the shooting lens, which can advance and retract, and which allows the shooting lens to adjust the focal length and the focus when the lens barrel is advanced,

wherein the lens barrel comprises a lens advancing/retracting mechanism which retracts at least one of the lens groups from a shooting optical axis when the lens barrel is retracted, and which advances the lens group retracted when the lens barrel is retracted to the shooting optical axis when the lens barrel advances, and

wherein the shooting lens forms a fixed focus shooting optical system by the remaining lens group among the plurality of lens groups excluding the lens group retracted from the shooting optical axis when the lens barrel is retracted.

16. The image taking apparatus according to claim 15 , wherein the shooting lens comprises three groups, i.e., a front lens group having a positive refractive force, a rear lens group having a negative refractive force and a focus lens having a positive refractive force arranged in this order from forward of the optical axis direction, the focal length of the shooting lens can be changed, and the focus is adjusted by moving the focus lens,

wherein the lens advancing/retracting mechanism retracts the rear lens group from the shooting optical axis when the lens barrel is retracted, and the shooting lens forms a fixed focus shooting optical system by the front lens group and the focus lens when the lens barrel is retracted.

17. The image taking apparatus according to claim 15 , wherein the shooting lens comprises two lens groups, i.e., a front lens group and a rear lens group,

wherein the lens barrel includes the lens advancing/retracting mechanism which allows a first lens group comprising one of the two lens groups to retract from the shooting optical axis when the lens barrel is retracted, and allows the first lens group retracted when the lens barrel is retracted to advance to the shooting optical axis when the lens barrel is advanced, and

wherein the shooting lens forms a fixed focus shooting optical system by a second lens group of the two lens groups when the lens barrel is retracted.

18. The image taking apparatus according to claim 17 , wherein the lens barrel further comprises a correction lens which advances on the shooting optical axis and corrects aberration of the second lens group when the lens barrel is retracted, and which retracts from the shooting optical axis when the lens barrel is advanced, and

wherein the shooting lens forms a fixed focus shooting optical system by the second lens group and the correction lens when the lens barrel is retracted.

19. The image taking apparatus according to claim 17 , wherein the lens barrel retracts the front lens group from the shooting optical axis when the lens barrel is retracted, and advances the front lens group to the shooting optical axis when the lens barrel is advanced.

20. The image taking apparatus according to claim 15 , wherein the shooting lens comprises four lens groups, i.e., a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in this order from forward of the optical axis direction,

wherein the lens barrel comprises a lens advancing/retracting mechanism which retracts at least one of the third lens group and the fourth lens group from the shooting optical axis when the lens barrel is retracted, and which advances the lens group retracted when the lens barrel is retracted to the shooting optical axis when the lens barrel advances, and

wherein the shooting lens forms a shooting optical system by the remaining lens group among the four lens groups excluding the lens group retracted from the shooting optical axis when the lens barrel is retracted.

21. The image taking apparatus according to claim 20 , wherein the lens advancing/retracting mechanism retracts both the second lens group and the fourth lens group from the optical axis when the lens barrel is retracted, and advances the second lens group and the fourth lens group retracted from the optical axis when the lens barrel advances, and

wherein the shooting lens forms a shooting optical system by the remaining lens group among the four lens groups excluding the second lens group and the fourth lens group retracted from the shooting optical axis when the lens barrel is retracted.

22. The image taking apparatus according to claim 20 , wherein the shooting lens forms a fixed shooting optical system by the remaining lens group when the lens barrel is retracted.

23. The image taking apparatus according to claim 20 , wherein the first lens group, the second lens group, the third lens group, and the fourth lens group have a positive refractive force, a negative refractive force, a positive refractive force, and a positive refractive respectively.

24. The lens barrel according to claim 1 , further comprising a lens barrier which covers a front surface of the shooting lens so as to be freely opened and closed.

25. The image taking apparatus according to claim 15 , further comprising a lens barrier which covers a front surface of the shooting lens so as to be freely opened and closed.

26. The lens barrel according to claim 24 , wherein the lens barrier is open when a picture is taken in the accommodated state.

27. The image taking apparatus according to claim 25 , wherein the lens barrier is open when a picture is taken in a state where the lens barrel is retracted.